HR: 14:10h
AN: T13H-03 INVITED    [Abstracts]
TI: Cenozoic tectonic evolution of Qaidam Basin: Structural geology, sedimentation, and implications for regional tectonic reconstruction of the Tibetan plateau
AU: * Yin, A
EM: yin@ess.ucla.edu
AF: UCLA, Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, United States
AU: Dang, Y
AF: Petro-China, Qinghai Oilfield Company, Dunhuang, 736202, China
AU: Chen, X
AF: Chinese Academy of Geological Sciences, Institute of Geomechanics, Minzhu Daxue Nanlu #11, Haidian District, Beijing, 100081, China
AU: Zhang, M
AF: Petro-China, Qinghai Oilfield Company, Dunhuang, 736202, China
AU: Wang, L
AF: Petro-China, Qinghai Oilfield Company, Dunhuang, 736202, China
AU: McRivette, M W
AF: UCLA, Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, United States
AB: Qaidam basin is the largest topographic depression inside the Tibetan plateau. Regional seismic-reflection profiles reveal its first-order structure as a broad Cenozoic synclinorium, with amplitude decreasing from greater than 16 km in the west to less than 4 km in the east. The synclinorium has expanded progressively eastward across the Qaidam region: starting from the west at 65-50 Ma to the east at about 24 Ma. Its formation was induced by an older thrust system initiated at 65-50 Ma in the north and a younger thrust system initiated at 29-24 Ma in the south. Cenozoic upper-crustal shortening decreases eastward across basin, from greater than 48 percent in the west to less than 1 percent in the east. This observation has two implications: (1) the southern Qaidam margin has rotated clockwise relative to the northern Qaidam margin for about 12 degrees, and (2) the crustal-thickening mechanism shifts progressively from dominantly upper-crustal shortening in the west to dominantly lower-crustal shortening in the east because the elevation and crustal thickness of the basin are rather constant. The diachronous initiation of thrusting in the northern and southern margins of Qaidam basin and the existing inference that the uplift of the Eastern Kunlun Range began at or after 30-20 Ma imply that the Paleogene (65-24 Ma) Qaidam basin and the coeval Hoh Xil basin were once parts of a single topographic depression bounded by the Fenghuo Shan thrust belt in the south and the Qilian Shan thrust belt in the north. The development of this large basin, similar in size to the modern Tarim basin north of Tibet, and its subsequent destruction may have been controlled by pre-existing weakness in the Tibetan lithosphere, creating a highly irregular sequence of deformation across Tibet during Indo-Asian collision.
DE: 8100 TECTONOPHYSICS
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting